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4.19 Physical Lights

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    Bumping this for visibility as the issues are still not resolved.
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      Bump. We need Documentation on the new Physical lighting system on 4.20, if its even working as intended.

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        Originally posted by rosegoldslugs View Post
        What is the issue that you guys are still having? There's a lot of talk here that isn't directly correlated to "4.19 physical lights" and I don't want to go through 8 pages again.

        I recently did a relighting scene with physical units(cd/m² for emissives/sky and Lumens for lights) and it felt pretty good. Like my first tests with the system, I avoided auto-exposure, so I can't speak on that. Although, a quick test with the Basic Auto Exposure with the Constant Calibration(amazing feature btw, simplifies exposure tweaking drastically) proved to be just as useful with all physical values than it was without them. I usually have Pre-Exposure enabled as well. Otherwise EV100 has been working pretty well.
        Meant to ask, are you going to do a breakdown of that scene or kinda show some insight to how your handling it? I been wondering about the constant calibration and Ev100.

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          Found This in 80lv today

          https://80.lv/articles/setting-light...l-engine-4-20/

          maybe offers some insight on the topic, haven't read it myself, gonna look at it tomorrow, but seems to be on the topic.

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            Looks similar to Daedalus methos tho.

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              Originally posted by Juanmilanese View Post
              Looks similar to Daedalus methos tho.
              Agreed. Very similar to what he would do.

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                Originally posted by KysgX View Post

                Meant to ask, are you going to do a breakdown of that scene or kinda show some insight to how your handling it? I been wondering about the constant calibration and Ev100.
                Constant Calibration just forces the auto-exposure to always adjust for a particular gray, like most auto-exposure in cameras do for 12%, 16% or 18% gray. It'll work for physical values as well, you just need to increase the Max value(~10,000) to allow for the high dynamic range physical values will require. EV is just a simplified way of measuring exposure that is always the same regardless of camera settings because it includes the necessary ISO, shutter speed, and f-stop settings. EV 10 would be identical at any ISO provided you also used the appropriate shutter speed and f-stop on the chart. The best part about it for our lighting is that just like physical units of measurements, EV is a known "measurement" and there are numerous charts out there to explain what value works best in any given lighting condition. Therefore making it a consistent way of getting close to perfect exposure for a given view. The 100 in the name is just part of the common convention of 100 ISO.


                Originally posted by KysgX View Post

                Agreed. Very similar to what he would do.
                Similar because that's what physical units brings to the workflow: consistency.

                That's my write-up btw.
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                  I consider the new lighting management very interesting. Of course the use of the new features is not so immediate and probably the choice was determined by the new road taken.

                  Epic Games is an American software house and perhaps did not take into consideration the conversion of the international system of measurement units using, instead, the American one.

                  In the United States, an old lighting unit that is not part of the SI system (= International System of Units: https://en.wikipedia.org/wiki/Intern...ystem_of_Units) is still used: the footcandle (literally "foot-candle"). It has:

                  1 footcandle = 10.764 lux,
                  1 lux = 0.0929 footcandle.

                  Now I share two links to the two units of measurement:
                  Candle= https://en.wikipedia.org/wiki/Candela
                  Lumen= https://en.wikipedia.org/wiki/Lumen_(unit)

                  I also found some difficulties with the new system, and to better understand the new features I read this information about the unit system and it was at least very useful for me.

                  I hope my post can be useful.
                  Thank you


                  Update

                  Luminous intensity :candela:[cd=lm/sr]
                  Luminous power :lumen: [lm=cd*sr]
                  Illuminance: [lux=lm/m²]
                  Luminance: [L=cd/m²]

                  the light of the Sun on average varies between 32 000 lx (32 klx) and 100 000 lx (100 klx);
                  in the spotlight of the television studios there are about 1 000 lx (1 klx);
                  in a luminous office there are about 400 lx;
                  in an illuminated office according to the current European Uni En 12464 there are 500 lx
                  the reflected light of the full moon is about 1 lx;
                  the light of a bright star is only 0.00005 lx (50 μlx).

                  A very good information of Exposure Triangle: Aperture, ISO and Shutter Speed on this article: https://www.cambridgeincolour.com/tu...a-exposure.htm
                  More information on Exposure Value: https://en.wikipedia.org/wiki/Exposure_value
                  Last edited by Tyr-el; 07-15-2018, 05:31 AM.

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                    Originally posted by Kalvothe View Post
                    Hey guys,
                    I have pinged some of our teams on this. We're in the thick of getting stuff ready for 4.20 so give us some time to put together a response. I know you've been waiting patiently and I promise I'll stay on top of it, but I ask for a bit more time.

                    :-)

                    Thanks!
                    Hello,

                    Now that 4.20 is out can we expect a reply on this thread?

                    This video sums up the issues detailing why and how the physical lighting is broken: https://forums.unrealengine.com/comm...46#post1475346
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                      Just got 4.20 and gave it a spin.

                      Going with sunny 16, you'll want something like 900,000 Lumens for simple room point light.
                      There are two new options added to PPV, "Maximum Aperture" and "Number of Diaphram Blades" which you can't use because they're both grayed out.


                      It's very strange I have to say, that Epic adds two new options to physical lighting system as if the system is usable and they're upgrading it.
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                        Originally posted by Maximum-Dev View Post
                        Just got 4.20 and gave it a spin.

                        Going with sunny 16, you'll want something like 900,000 Lumens for simple room point light.
                        There are two new options added to PPV, "Maximum Aperture" and "Number of Diaphram Blades" which you can't use because they're both grayed out.


                        It's very strange I have to say, that Epic adds two new options to physical lighting system as if the system is usable and they're upgrading it.


                        Are you trying to view a standard light bulb outside? Otherwise the sunny 16 rule doesn't seem reasonable for an interior, to me. It's specifically for subjects directly in a bright sunlight and the "rule" varies based on the surrounding area of the subject. Even so, I wouldn't expect to see a typical interior lightbulb outside, but what you see from the light source greatly depends on the position of the light(inverse square falloff) and the brightness of the surface it is hitting.

                        Those 2 options are used when you're viewing through a CineCamera.
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                          Originally posted by rosegoldslugs View Post



                          Are you trying to view a standard light bulb outside? Otherwise the sunny 16 rule doesn't seem reasonable for an interior, to me. It's specifically for subjects directly in a bright sunlight and the "rule" varies based on the surrounding area of the subject. Even so, I wouldn't expect to see a typical interior lightbulb outside, but what you see from the light source greatly depends on the position of the light(inverse square falloff) and the brightness of the surface it is hitting.

                          Those 2 options are used when you're viewing through a CineCamera.
                          When you setup sunny 16 for outdoor you can't change it for interiors. If you go with a reasonable exposure for interior you can't change it when you get outside so is there any correct workflow here at all?
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                            Originally posted by Maximum-Dev View Post

                            When you setup sunny 16 for outdoor you can't change it for interiors. If you go with a reasonable exposure for interior you can't change it when you get outside so is there any correct workflow here at all?
                            Can't you use two different Post-Process Volumes with the respective EV settings? It's a little more work, since we can't assign actual EV values like in the viewport, but all the proper settings are there to match what EV is based on.

                            For simplicity, since I don't think it has any effect other than offsetting the necessary shutter speed/f-stop right now, you can just leave it at the default ISO of 100. For instance, EV16 at ISO 100 would require f/16 and a shutter speed of 1/100 or 1/125.


                            Edit: If you want automatic exposure, I'm a big fan of the change to the Basic method where it automatically adjusts for a particular gray(default is 16%, cameras typically go for 12% to 18%). If you use physical values for your lights, you'll need to increase the Max Range to around 10,000. You could also enable Pre-Exposure to improve the quality of the exposure adjustment and fix any artifacts from the high values, but that will break the reading in the Pixel Inspector. Any other adjustments needed for particular areas can be done with the exposure compensation per Post-Process Volume.
                            Last edited by rosegoldslugs; 07-26-2018, 01:51 PM.
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                              Originally posted by rosegoldslugs View Post

                              Can't you use two different Post-Process Volumes with the respective EV settings? It's a little more work, since we can't assign actual EV values like in the viewport, but all the proper settings are there to match what EV is based on.

                              For simplicity, since I don't think it has any effect other than offsetting the necessary shutter speed/f-stop right now, you can just leave it at the default ISO of 100. For instance, EV16 at ISO 100 would require f/16 and a shutter speed of 1/100 or 1/125.


                              Edit: If you want automatic exposure, I'm a big fan of the change to the Basic method where it automatically adjusts for a particular gray(default is 16%, cameras typically go for 12% to 18%). If you use physical values for your lights, you'll need to increase the Max Range to around 10,000. You could also enable Pre-Exposure to improve the quality of the exposure adjustment and fix any artifacts from the high values, but that will break the reading in the Pixel Inspector. Any other adjustments needed for particular areas can be done with the exposure compensation per Post-Process Volume.
                              We have approximately 80 houses within just 1x1 Km area, we can't really use one PPV per house for correcting the interior exposure. Other issue with that method is that if I want to make a change to interior PPV, for the sake of consistency I'd have to do it for every other PPV as well (and our actual game world contains hundreds of interiors).
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                                Originally posted by Maximum-Dev View Post
                                if I want to make a change to interior PPV, for the sake of consistency I'd have to do it for every other PPV as well (and our actual game world contains hundreds of interiors).
                                been wondering forever why PPVs cannot be blueprinted...
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